title: Monosome formation during translation initiation requires the serine/arginine-rich protein Npl3.
abstract: The yeast shuttling serine/arginine-rich protein Npl3 is required for the export of mRNAs and pre-60S ribosomal subunits from the nucleus to the cytoplasm. Here, we report a novel function of Npl3 in translation initiation. A mutation in its C terminus that prevents its dimerization (npl3Δ100) is lethal to cells and leads to translational defects, as shown by [(35)S]methionine incorporation assays and a hypersensitivity to the translational inhibitor cycloheximide. Moreover, this Npl3 mutant shows halfmers in polysomal profiles that are indicative of defects in monosome formation. Strikingly, the loss of the ability of Npl3 to dimerize does not affect mRNA and pre-60S export. In fact, the mRNA and rRNA binding capacities of npl3Δ100 and wild-type Npl3 are similar. Intriguingly, overexpression of the dimerization domain of Npl3 disturbs dimer formation and results in a dominant-negative effect, reflected in growth defects and a halfmer formation phenotype. In addition, we found specific genetic interactions with the ribosomal subunit joining factors Rpl10 and eukaryotic translation initiation factor 5B/Fun12 and detected a substantially decreased binding of npl3Δ100 to the Rpl10-containing complex. These findings indicate an essential novel function for Npl3 in the cytoplasm, which supports monosome formation for translation initiation.
authors.affiliation: Abteilung für Molekulare Genetik, Institut für Mikrobiologie und Genetik, Göttinger Zentrum für Molekulare Biowissenschaften, Georg-August Universität Göttingen, Göttingen, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Baierlein
authors.forename: Alexandra
authors.initials: A
authors.lastname: Hackmann
authors.forename: Thomas
authors.initials: T
authors.lastname: Gross
authors.forename: Lysann
authors.initials: L
authors.lastname: Henker
authors.forename: Frederik
authors.initials: F
authors.lastname: Hinz
authors.forename: Heike
authors.initials: H
authors.lastname: Krebber
mesh_terms: D015825:Chromosomes, Fungal / Q000235:genetics* / Q000378:metabolism; D050296:Microbial Viability; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D009687:Nuclear Proteins / Q000737:chemistry / Q000502:physiology*; D010442:Peptide Chain Initiation, Translational; D054730:Protein Interaction Domains and Motifs; D025941:Protein Interaction Mapping; D055503:Protein Multimerization; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000502:physiology*; D012269:Ribosomal Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*
chemical_list: C077734:NPL3 protein, S cerevisiae; D009687:Nuclear Proteins; D016601:RNA-Binding Proteins; C093333:RPL10 protein, S cerevisiae; D012269:Ribosomal Proteins; D029701:Saccharomyces cerevisiae Proteins